For unknown reasons the bus ended up with its passengers -- elderly and disabled adults -- atop the tracks at Maple Avenue in Evans City around 8:10 a.m., when the 31-car train slammed into its driver's side, knocking the vehicle askew and totaling it.

Two critically injured passengers were flown by medical helicopter to Pittsburgh-area hospitals. One of them, 91-year-old Claudette Miller of Callery, died at Allegheny General Hospital at 1:02 p.m., according to the Allegheny County medical examiner's office.

Bus-train collision in Evans City injures several

Two people were critically injured this morning when a train crashed into a Butler Area Rural Transit Authority bus at a train crossing in Evans City. (Video by Darrell Sapp; edited by Melissa Tkach)

The other remained in critical condition, and Evans City police Chief Joseph McCombs said the passenger might not survive.

Everyone else on the bus, including the driver -- identified by Chief McCombs as Frank Schaffner, 59, of Butler -- was taken by ambulance to hospitals in Allegheny and Butler counties. Hospital officials said their injuries were not life-threatening.

Conflicting accounts emerged about whether the driver was stopped or in the process of crossing the tracks when the crash occurred. Also unclear was the role the fog played.

"For some unknown reason, it stopped directly in the crossing," Chief McCombs said of the bus. Police said the train's engineer told them he sounded the horn "numerous times."

Chief McCombs said the bus, which was going east toward South Washington Street, entered the crossing and did not move as the Allegheny Valley Railroad train -- composed of two locomotives and 29 cars -- was approaching.

PG graphic: Crash near Evans City(Click image for larger version)

The train was believed to be moving around 25 mph -- the speed limit -- according to information provided to federal inspectors by the engineer and conductor.

The engineer saw the bus, sounded the horn several times and applied the brakes before the crash, which Chief McCombs described as "pretty chaotic" with "pretty severe impact."

Michael Robb, executive director of the Alliance for Nonprofit Resources Inc., which oversees the program under whose auspices the passengers were being transported, relayed a different version of events.

"I don't believe the bus stopped on the train tracks at all. He stopped prior to the tracks as he's required and as he was crossing the tracks he was hit," Mr. Robb said.

"It really is at the driver's discernment whether a train was coming. I do not know if the train blew the whistle or not. All I know is that our driver was conscious enough to give his report to local authorities that he stopped. As he was crossing he was struck by the train."

Mr. Robb said he had not spoken to the driver. He expressed sympathy to the victims and said transportation services will continue.

Evans City police said they executed a search warrant to test the driver's blood to try to determine whether drugs or alcohol were a factor. The chief said the driver did not display any obvious signs of intoxication.

The Federal Railroad Administration, which sent three inspectors to the scene, said it is up to the owner of the road -- in this case, Evans City -- to decide whether to install traffic control devices at the crossing.

"Towns and state [departments of transportation] work with railroads on the design, but it's ultimately up to them to decide to spend the money for active control devices," agency spokesman Rob Kulat said.

Pennsylvania Department of Transportation spokesman Steve Chizmar said it was a "collaborative effort" among the municipality, the state, the federal government and the track owner to determine whether warning devices should be installed.

Evans City Mayor Dean Zinkhann said he was unclear about who was responsible for determining the type of warning used at a crossing. Chief McCombs, meanwhile, indicated that the track's owner, Buffalo & Pittsburgh Railroad, would determine the placement of crossing signals.

A marketing director for that company did not return a phone message Friday.

Mr. Zinkhann said the crossing in question leads to a remote area with two or three houses. He estimated that cars cross the tracks there eight to 10 times a day at most.

"I don't know who the fault is or the blame is [with]," the mayor said. "It would be nice if there were more warning, yes."

A search of federal records found no other accidents at the crossing.

The paratransit vehicle -- a 2011 or 2012 Ford van chassis with a cutaway bus on top of it -- was transporting older and mentally disabled adults, ranging in age from mid-20s to 91.

It is owned by Butler County and is used for the Butler Area Rural Transit program, which is administered by the Alliance for Nonprofit Resources.

Seat belts likely prevented more serious injuries, according to the sister of one of the passengers.

The woman, a Cranberry resident, said her brother and other passengers all were strapped into their seats at the time of the accident. She asked that neither her name nor that of her brother be used.

While on its morning run Friday, the bus apparently encountered fog at the railroad crossing.

"There was very heavy fog in the area when we arrived," said Brian Greenawalt, Harmony paramedic supervisor. "We're not sure whether that contributed."

"One-tenth of a mile is all they could see," Mr. Zinkhann said, referring to the morning's visibility. "I don't know why they didn't hear [the train]. The train was alerting and signaling and horn tooting."

Authorities believe the fog might have led to the accident, according to Mr. Robb.

He said he received his information from police at the scene.

Investigators have uploaded data from the train's "black box" recorder for analysis. The data available should include the train's speed, direction, throttle position, use of brakes, signals received from the dispatcher and use of the horn.

The federal Train Horn Rule requires locomotive engineers to sound train horns between 15 and 20 seconds in advance of all "public grade crossings" in most circumstances.

Russell A. Peterson, chief executive officer of Oakmont-based Carload Express Inc., which operates the Allegheny Valley Railroad, wrote in an email: "It's a very sad day for all involved and our hearts and prayers go out to the passengers on the bus and the crew on the train."

Mr. Robb said the bus driver was a part-time employee and had worked for his group for about 21/2 years and had a good driving record.

Mr. Robb said the man also works part time as an ambulance driver.

"He's been a good driver for us. No incidents with him as a driver to my knowledge," Mr. Robb said. "I feel comfortable with his familiarity with the rules."